The present invention relates generally to a fiber optic connector and, more particularly, to a ferrule and a fiber optic connector housing having enlarged shoulders to provide improved registration therebetween.
Fiber optic connectors include a connector housing defining a lengthwise extending internal cavity and a ferrule disposed at least partially within the internal cavity defined by the connector housing. In addition to the ferrule and the connector housing, a fiber optic connector typically includes a crimp body connected to a rear portion of the connector housing and a spring disposed between the crimp body and the rear surface of the ferrule for urging the ferrule forwardly in the internal cavity defined by the connector housing. A fiber optic connector also typically includes a crimp band for cooperating with the crimp body to engage one or more strength members of an optical cable to securely attach the fiber optic connector to the fiber optic cable, as well as a connector boot for providing strain relief for the optical fibers. In addition, a fiber optic connector can include one or more optional components, such as a pin keeper, a spring centering element, a lead-in tube, and a divider as known to those skilled in the art.
Most ferrules, including both single-fiber ferrules and multifiber ferrules, include a ferrule body having a lengthwise extending shaft and an enlarged rear portion. Since the rear portion is larger in lateral cross-section than the shaft, conventional ferrules define a shoulder that extends circumferentially about the ferrule body.
One common type of multifiber connector is an MTP connector such as described by U.S. Pat. No. 5,214,730 to Shinji Nagasawa et al. that issued on May 25, 1993, and is assigned to Nippon Telegraph and Telephone Corporation of Tokyo, Japan. A conventional MTP connector includes an MT multifiber ferrule having a generally rectangular shape in lateral cross-section. In this regard, an MT ferrule typically has a shaft that has a rectangular cross-sectional shape and an enlarged rear portion that also has a rectangular cross-sectional shape. Since the rear portion of an MT ferrule is larger than the shaft, the resulting shoulder also has a rectangular shape, and extends circumferentially about the shaft.
Similarly, the connector housings of most fiber optic connectors, including MTP connectors, also define an inwardly projecting shoulder. In this regard, a conventional connector housing generally defines an internal cavity having forward and rearward segments in which the rearward segment is larger in lateral cross-section than the forward segment. As such, conventional connector housings also define a shoulder at the intersection of the forward and rearward segments.
Since the connector housing of an MTP connector is specifically designed to receive an MT ferrule, the internal cavity defined by the connector housing generally has a rectangular shape in lateral cross-section in order to match the shape of the MT ferrule. As such, the shoulder defined by the connector housing between the forward and rearward segments of the internal cavity also generally has a rectangular shape. In order to assemble an MTP connector, the ferrule is inserted through the rear end of the connector housing and into its internal cavity. The ferrule is then advanced forwardly through the internal cavity until its shoulder contacts and engages the shoulder of the connector housing. Once the two shoulders are engaged, the shaft of the ferrule extends into the forward segment of the internal cavity, while the enlarged rear portion of the ferrule is retained within the rearward segment of the internal cavity.
While it is important for the respective shoulders of the ferrule and connector housing to engage to limit the amount by which the ferrule can protrude beyond the connector housing, fiber optic connectors are also designed such that the ferrule is capable of floating within the connector housing. By floating, the ferrule can move somewhat from side to side relative to the connector housing in order to facilitate alignment when the fiber optic connector is mated, such as with another fiber optic connector. As such, the forward segment of the housing""s internal cavity generally has a slightly larger cross-sectional area than the shaft of the ferrule. Likewise, the rearward segment of the internal cavity also generally has a larger cross-sectional area than the rear portion of the ferrule.
As a result of its rectangular shape in lateral cross-section, an MT ferrule generally has a pair of opposed major sides and a pair of opposed minor sides, with the major sides being broader or wider than the minor sides. In order to maximize the float afforded to a ferrule within the connector housing of an MTP connector, some connector housings are designed such that the inwardly projecting shoulder only engages the shoulder defined by the ferrule along the opposed minor sides and does not engage the shoulder defined by the ferrule along the major sides.
In order to further maximize the. float afforded to the ferrule, the forward segment of the internal cavity of an MTP connector is typically sized as large as possible relative to the MT ferrule. As shown in FIG. 1, the difference between the width f of the opening defined by the shoulder 10 of the connector housing 12 and the width w of the shaft 14 of the ferrule 16 is typically equal to about one-half of the difference in the width s of the enlarged rear portion 18 of the ferrule and the width w of the shaft portion of the ferrule. As such, the opposed minor sides of the shoulder 16a defined by the ferrule are both generally engaged by the shoulder of the connector housing. In instances in which the forward segment of the internal cavity is chamfered such that most portions of the forward segment are larger than the opening defined by the shoulder between the forward and rearward segments, the shoulder of the ferrule can become dislodged from the inwardly protruding shoulder of the connector housing. In this instance, the ferrule would assume a cocked position as shown in FIG. 2 so the ferrule is no longer aligned with the connector housing. As a result of the bias force introduced by the spring that urges the ferrule forward, the ferrule will typically remain in the cocked position, thereby preventing mating of the optical fibers.
A ferrule is therefore provided according to one embodiment of the invention that defines a shoulder having curved corners. In addition, a fiber optic connector housing is provided according to another embodiment of the present invention that defines an inwardly projecting shoulder having curved corners. By including shoulders having curved corners, the fiber optic connector of the present invention allows the ferrule to float within the internal cavity defined by the connector housing without becoming dislodged and assuming a cocked position within the internal cavity. As such, the fiber optic connector of the present invention maintains the ferrule in an aligned position relative to the connector housing such that the optical fibers upon which the ferrule is mounted can be optically interconnected with other optical fibers.
According to one embodiment, a ferrule is provided that includes a lengthwise extending shaft and an enlarged rear portion proximate the shaft. The rear portion is larger in lateral cross-section than the shaft-to thereby define a shoulder. While that portion of the shaft proximate the enlarged rear portion includes curved corners such that the shoulder has corresponding curved inner corners, that portion of the shaft proximate the enlarged rear portion is not cylindrical but, instead, includes at least one linear edge extending between a pair of the curved corners. In this regard, both the lengthwise extending shaft and the enlarged rear portion preferably define a substantially rectangular shape such that the resulting shoulder also has a substantially rectangular shape, albeit with curved inner corners.
In one advantageous embodiment, the curved corners are semicircular in shape. In this embodiment, the semicircular corners can define an interior angle of 90xc2x0 and a radius of about 1 millimeter. Alternatively, the curved corners can be elliptical in shape. In one embodiment, the enlarged rear portion also includes curved corners. According to this embodiment, the curved corners of both the shaft and the enlarged rear portion are semicircular in shape. In this regard, the semicircular corners of the enlarged rear portion preferably define a smaller radius than the semicircular corners of the shaft.
According to another embodiment of the present invention, a fiber optic connector housing is provided that includes a forward segment defining a lengthwise extending passage and a rearward segment also defining a lengthwise extending passage. The lengthwise extending passages defined by the forward and rearward segments are in communication. However, the lengthwise extending passage defined by the rearward segment is larger in lateral cross-section than the lengthwise extending passage defined by the forward segment. As such, a shoulder is defined at the intersection of the forward and rearward segments. According to this embodiment, that portion of the forward segment proximate the rearward segment defines a section of the lengthwise extending passage having curved corners and at least one linear edge extending between the pair of curved corners. In this regard, the lengthwise extending passage defined by the forward segment preferably has a substantially rectangular shape in lateral cross-section.
According to one embodiment, the curved corners of that portion of the forward segment proximate the rearward segment are semicircular in shape. In this regard, the semicircular corners can define an interior angle of 90xc2x0 and have a radius between about 0.5 millimeters and 0.7 millimeters. Alternatively, the corners can be elliptical in shape.
According to either embodiment, the ferrule will be permitted to float somewhat within the internal cavity defined by the connector housing. By designing the ferrule and/or the connector housing such that at least one shoulder has curved corners, the shoulders of the ferrule and the connector housing remain in contact and in engagement even as the ferrule floats within the internal cavity defined by the connector housing. As such, the ferrule remains in an aligned position within the connector housing and is prevented from becoming cocked within the internal cavity as would occasionally occur with conventional fiber optic connectors in which the shoulder of the ferrule would slip off of the inwardly projecting shoulder of the connector housing.